1. Field of the Invention
The present invention relates in general to a cooling system equipped in a motor vehicle, and more particularly to a cooling system which is powered by a vacuum created in an air induction part of an internal combustion engine of the vehicle.
2. Description of the Prior Art
Nowadays, some passenger motor vehicles are equipped with a cooler box for cooling any goods, such as fruits, juice cans, wet towels and the like. Usually, the cooler boxes hitherto proposed are of a type which is powered by an automotive air conditioner equipped in the motor vehicle.
One of the cooling systems for such conventional cooler boxes is disclosed in Japanese Patent First Provisional Publication No. 59-48220, which, as is shown in FIG. 5 of the accompanying drawings, is arranged in a bypass circuit "C" of a known passenger room cooling system "A". The passenger room cooling system "A" comprises generally a compressor 10 driven by the engine of the vehicle for compressing a coolant, a condenser 12 for condensing and thus liquidizing the coolant from the compressor 10, an expansion valve 14 which opens when the pressure in the coolant line upstream of the expansion valve 14 comes to a predetermined degree, and an evaporator 16 for evaporating the coolant from the expansion valve 14. The coolant from the evaporator 16 is returned to the compressor 10 for recirculation of the coolant in the system "A". Due to heat exchange carried out at the evaporator 16, air blown into the passenger room is cooled. Although not shown in the drawing, a heater unit is usually provided near the evaporator 16 to constitute an air conditioning system.
The cooling system for the cooling box "B" comprises an auxiliary expansion valve 18 into which a part of the coolant from the condenser 12 is fed, and an auxiliary evaporator 20 for evaporating the coolant from the expansion valve 18. The coolant discharged from the evaporator 20 is returned to the compressor 10. The cooling box "B" is arranged to house therein the auxiliary evaporator 20, so that under flowing of the coolant in the bypass circuit "C", the interior of the cooler box "B" is cooled.
However, due to its inherency in construction, the cooling system of the cooler box "B" of the above-mentioned type can not operate when the room cooling system "A" is in its OFF condition. That is, the operation of the cooler box cooling system is only available when the room cooling system is ON condition. This is very disadvantageous when considering a usage of the cooler box "B" in winter. In fact, in winter, there is no need of operating the room cooling system "A".